Get rid of extensions dependency from content\browser.

content/common/notification_type.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_COMMON_NOTIFICATION_TYPE_H_
 #define CONTENT_COMMON_NOTIFICATION_TYPE_H_
 #pragma once
 
 // This file describes various types used to describe and filter notifications
 // that pass through the NotificationService.
@@ skipping 381 matching lines @@
     // to switching away from this tab.  The source is a Source<TabContents>.
     TAB_CONTENTS_HIDDEN,
 
     // This notification is sent when a TabContents is being destroyed. Any
     // object holding a reference to a TabContents can listen to that
     // notification to properly reset the reference. The source is a
     // Source<TabContents>.
     TAB_CONTENTS_DESTROYED,
 
     // This notification is sent when TabContents::SetAppExtension is invoked.
-    // The source is the TabContents SetAppExtension was invoked on.
+    // The source is the ExtensionTabHelper SetAppExtension was invoked on.
     TAB_CONTENTS_APPLICATION_EXTENSION_CHANGED,
 
     // A RenderViewHost was created for a TabContents. The source is the
     // associated TabContents, and the details is the RenderViewHost
     // pointer.
     RENDER_VIEW_HOST_CREATED_FOR_TAB,
 
     // Notification than an interstitial has become associated with a tab. The
     // source is the TabContents, the details not used.
     INTERSTITIAL_ATTACHED,
@@ skipping 945 matching lines @@
 };
 
 inline bool operator==(NotificationType::Type a, NotificationType b) {
   return a == b.value;
 }
 inline bool operator!=(NotificationType::Type a, NotificationType b) {
   return a != b.value;
 }
 
 #endif  // CONTENT_COMMON_NOTIFICATION_TYPE_H_